This invention relates to an x-ray apparatus for producing transversal layer images of a photographic subject, including an x-ray source, a diaphragm for condensing the x-rays into a narrow x-ray beam whose cross-sectional spread is equal to the thickness of the layer in a direction perpendicular to the layer and substantially equal to or less than the thickness of the layer in a direction parallel to the layer, and with a measuring arrangement for measuring the intensity of radiation which is impinged upon by the central ray of the x-ray beam, in which, for penetrating the subject from different directions, the x-ray source and the measuring arrangement are arranged together on a rotating frame which is rotatable through equidistant angular steps about a point situated on the central ray of the total radiation emanating from the x-ray tube and in which the measuring arrangement is mounted on the rotating frame on a carriage which is displaceable by a motor perpendicularly of the central ray and the axis of rotation, and further including a cumputer for determining the absorption values of the points of intersection of the radiation in the subject from the intensity of the radiation received by the measuring arrangement.
An x-ray apparatus of this type is described in U.S. Pat. No. 3,778,614. In this known x-ray apparatus, the x-ray tube is arranged on the same carriage as the measuring arrangement so that it is displaceable together with the measuring arrangement perpendicularly of the central ray of the x-ray beam and the axis of rotation. The diaphragm is stationary in relation to the x-ray tube. An x-ray tube is a relatively heavy component so that the mechanics involved in the mounting and displacement of the x-ray tube/measuring arrangement unit are relatively complicated. In addition, guide means are required for the high-tension lead to the x-ray tube to allow linear displacement of the x-ray tube during the scanning operation.